1. Field of the Invention
The present invention relates to a cap device having a cap that is screwed into a tank opening.
A fuel cap of conventional structure is screwed into a filler neck (opening formation member) by several rotations of a handle of the fuel cap. A ratchet mechanism is typically formed between a closer and the handle to run idle at a torque of not less than a preset level and thereby clamp a gasket with the preset torque. Multiple rotations of the handle are required to screw the fuel cap into the filler neck. The ratchet mechanism does not fix the position of the handle when the fuel cap is screwed into the filler neck. This leads to poor operation performance.
2. Description of the Related Art
A quick-turn cap has been proposed to solve the above problem (see, for example, JP No. 2000-142738A). In this proposed structure, a neck engagement projection with an insertion cut is formed on an inner wall of the filler neck, while a cap engagement projection is formed at a position of 180 degrees in a circumferential direction on an outer circumference of the cap. The cap engagement projection is fit into the insertion cut of the neck engagement projection and is rotated by approximately 180 degrees, so that the cap engagement projection engages with the neck engagement projection. This proposed structure further has a stopper formed on the inner wall of the filler neck to stop rotation of the cap and thereby fix the position of the handle. This proposed structure, however, has relatively complicated shape since the neck engagement projection and the stopper are formed on the inner wall of the filler neck. Fabrication of this structure is not easy especially when the filler neck is made of a metal pipe.